I´m away from any PC running Debian ( including my own ), so going blind here.

There was a recent split of debconf package into Py2 & Py3 versions ( changelog ) so it´s most likely related to that.Either the module was renamed ( thus the "import" fails ), or the package itself is not installed.

The split broke python3-debconf which had already been installed and used since the beginning of VSIDO

Why the dev would not take into account both needs and make one or both a dependency is beyond me...

Laziness?

Thanks again to filip for the help

No idea, though the split seems uneccessary to me. After all, both packages install the very same "debconf.py" ( it´s compatible with both Py´s ), just to different locations... Perhaps they wanted to drop Python dependencies from "debconf" package...